The present invention generally relates to a method and apparatus for unloading and feeding items from a tiered stack, pile, or the like. More particularly, the present invention relates to an apparatus for receiving, separating, and continuously feeding boards from a unit of lumber.
Manufacturing companies typically receive lumber boards in large units or bunks. Each unit or bunk consists of several dozen individual boards that are stacked in horizontal rows (or xe2x80x9ctiersxe2x80x9d) and vertical columns. A lumber unloading and feeding apparatus (xe2x80x9cbunkfeederxe2x80x9d) breaks down the units into individual boards and substantially continuously delivers the individual boards into another machine, such as an automatic or computer-controlled saw.
Because the bunkfeeder supplies other automatic machinery, it should be efficient and a reliable in its manipulation of the unit and in its delivery of individual pieces to the next processing station. The timing and sequencing of the breakdown process should be carefully considered and orchestrated to minimize interruptions in its output. The goal, generally, is to provide a substantially continuous output of individual boards. The bunkfeeder should also be capable of handling boards with different lengths, widths, and heights. This feature is particularly desirable when the bunkfeeder is used with computer controlled saws, because the manufacturer can use the same equipment to produce a variety of items. That is, the manufacturer can change its production by changing the size/length of boards to be fed and altering the commands given to the automatic saw and to the bunkfeeder. In addition, the bunkfeeder should be capable of handling units with different lengths, widths, heights, and number of boards.
U.S. Pat. No. 4,640,655 to Jacobsen, U.S. Pat. No. 4,838,748 to Johnson, and U.S. Pat. No. 5,249,915 to Ritola all disclose apparatuses for separating individual tiers from a tiered load. All three apparatuses pivot the unit into a load travel path, then advance the unit along the travel path toward a discharge point. At the discharge point, the top row of the load is allowed to slide down an inclined surface onto a conveyor belt. One problem with these devices, however, is that friction will cause some boards in the top row to stick to the adjacent row and release unexpectedly, which can lead to log jams at the bottom of the inclined surface. In addition, these apparatuses do not separate the individual boards and can spill the loads during their tilting step.
Accordingly, there is a need for a lumber unloading and feeding apparatus that can reliably break down units of lumber into individual boards. There is also a need for a lumber feeding apparatus that can receive different sized boards and different sized units.
The present invention provides a lumber unloading and feeding apparatus that can reliably separate individual boards from a stacked unit of lumber and that can feed the individual boards into other automatic machinery. One aspect of the present invention comprises an apparatus for separating items from the bottom of a tiered load. One embodiment of this apparatus comprises a first load supporting surface and a second load supporting surface that cooperate to support a first end and a second end of at least one tier; a tier receiver located below the first and second load supporting surfaces; a first pusher that biases the first end of the tier off the first load supporting surface; and a second pusher that biases the second end of the tier off the second load supporting surface, thereby allowing the tier to drop onto the tier receiver. The tier receiving surface in this embodiment is a conveyor adapted to bias a plurality of items against a stop. This embodiment further comprises a lifter that biases all but one unit in the plurality of units out of engagement with the conveyor, which allows the conveyor to bias the one remaining item into a discharge area.
Another aspect of the present invention is a method of separating items from a tiered load. One embodiment of this method comprises the acts of placing a plurality of tiers on a first load supporting surface and a second load supporting surface, the plurality of tiers including a first, bottom tier; pushing a first end of the first, bottom tier off the first load supporting surface; and pushing a second end of the first, bottom tier off the second load supporting surface, whereby the first, bottom tier drops onto a tier receiver. In this embodiment, the first, bottom tier may include a plurality of items and the method may further comprise the acts of collecting the first, bottom tier against a stop and allowing one item in the plurality of items past the stop.
Still another aspect of the present invention is a method of separating an item from a plurality of items. One embodiment comprises the acts of using the conveyor to bias the plurality of items against a stop; lifting all but one item in the plurality of items off the conveyor; and removing the stop, whereby the conveyor biases the one item into a discharge area. This method may be repeated as necessary to separate the remaining items.
The present invention provides numerous advantages over conventional unloading and feeding machines. For example, the present invention allows manufacturers to insert an entire unit of boards into the bunkfeeder as the unit is received from the mill. This reduces the labor necessary to operate other unloading and feeding machines. The present invention can also fit into a relatively small space and can be adjusted to accept both standard and non-standard sized units of lumber.